How can I focus on breath at the tip of my nose?

I have chosen to practice meditation *on* and mindfulness *of* the breath, at the tip of the nose, as prescribed by the Buddha. My difficulty, simply put, is that I am able to sense and focus on the breath everywhere ***BUT*** the tip of my nose! I suspect that focusing on where I *do* perceive it (in the nostrils) might be sufficient, but I want to precisely follow the instructions given by the Buddha. I came to notice on my own one day that projecting my attention onto a fixed location in the space in front of my head (with eyes closed) seemed to facilitate absorption in single-minded awareness. I had hoped that directing my awareness to the tip of my nose would produce similar results. Imagine my disappointment upon finding that I was unable to fixate my focus as the Buddha recommended! I will be very grateful for any guidance... May all beings find perfect freedom from dukkha and samsara!